cc: Add tile-free software compositing mode.

cc/layers/append_quads_data.h

Index: cc/layers/append_quads_data.h
diff --git a/cc/layers/append_quads_data.h b/cc/layers/append_quads_data.h
index 1ec8184a17aa225e9b898c47f4e70e0f75304b61..7e2dc68e3c756a9cbe0f3c1a83adced932fecdd0 100644
--- a/cc/layers/append_quads_data.h
+++ b/cc/layers/append_quads_data.h
@@ -12,17 +12,21 @@ namespace cc {
 
 struct AppendQuadsData {
   AppendQuadsData()
-      : had_occlusion_from_outside_target_surface(false),
+      : allow_tile_draw_quads(true),
+        had_occlusion_from_outside_target_surface(false),
         had_incomplete_tile(false),
         num_missing_tiles(0),
         render_pass_id(0, 0) {}
 
   explicit AppendQuadsData(RenderPass::Id render_pass_id)
-      : had_occlusion_from_outside_target_surface(false),
+      : allow_tile_draw_quads(true),
+        had_occlusion_from_outside_target_surface(false),
         had_incomplete_tile(false),
         num_missing_tiles(0),
         render_pass_id(render_pass_id) {}
 
+  // Set by LayerTreeHostImpl.
+  bool allow_tile_draw_quads;
   // Set by the QuadCuller.
   bool had_occlusion_from_outside_target_surface;
   // Set by the layer appending quads.